The typical conformations of semi-flexible polymers depend on the spatial
scale, on which they are observed.
On molecular scales, these polymers behave as semi-rigid rods that keep their spatial
orientation up to the so-called persistence length. On larger length scales,
the polymers loose their orientation
and attain random coil conformations. This behavior implies a
renormalized, scale-depending bending stiffness that decays to zero on large scales
When a weak stretching force is applied to a semi-flexible polymer, it primarily
acts to reduce the amplitude of thermally excited shape fluctuations. A strong stretching
force, on the other hand, probes the molecular bonds between the monomers or subunits of the polymer.
The full range of forces is covered by the
semi-flexible harmonic chain model
was originally introduced for the hydrocarbon tails of lipid molecules
When a compressive force is applied, the semi-flexible polymer undergoes a
buckling (or Euler) instability at a critical buckling force, which is also affected by thermal fluctuations
A rather interesting class of semi-flexible polymers is provided by oligo- and polysaccharides. Even though the backbone of an oligosaccharide assumes an essentially straight conformation in the absence of external forces, it can be easily bent by forces of physiological magnitude as revealed by atomistic Molecular Dynamics simulations [6, 7].
Conformational diversity of O-antigen polysaccharides of the gram-negative bacterium Shigella flexneri serotype Y.
Conformational diversity of O-antigen polysaccharides ... - Supporting Information
J. Phys. Chem. B 118, 2523-2534 (2014).
Mechanical compressibility of the Glycosylphosphatidylinositol (GPI) anchor backbone governed by independent glycosidic linkages.
JACS 134, 18964-18972 (2012)
Modelling semiflexible polymers: Shape analysis, buckling instabilities, and force generation.
Soft Matter 6, 5764-5769 (2010).
Stretching of buckled filaments by thermal fluctuations.
Phys. Rev. E 76, 061914 (2007).
Persistence length of semiflexible polymers and bending rigidity renormalization
Europhys. Lett. 76, 994 - 1000 (2006).
Buckling, Bundling, and Pattern Formation: From Semi-Flexible Polymers to Assemblies of Interacting Filaments.
J. Comput. Theor. Nanosci. 3, 1 - 14 (2006).
Stretching of semiflexible polymers with elastic bonds.
Eur. Phys. J. E 14, 17-34 (2004).
Computer simulations of bilayer membranes: Self-assembly and interfacial tension.
J. Chem. Phys. 108, 7397-7409 (1998).
Shape fluctuations and critical phenomena
In H.~van Beijeren, editor, ''Fundamental Problems in Statistical Mechanics'', Vol. VII
Elsevier Science Publishers (1990).